1. Technical Field
The present invention relates to the field of animal training devices and in particular to radio controlled animal collars for providing electrical stimulation to the animal being trained in order to condition the animal's behavior.
2. Related Art
Radio-controlled animal training collars for conditioning an animals behavior through electrical stimulation are known. Conventional collars typically use a radio transmitter operated by a trainer to trigger an electrical circuit attached to an animal's collar. A radio receiver in the collar is coupled to the electrical circuit, which has a pair of electrodes positioned to contact the animal's skin. The receiver couples signals from the transmitter to the electrical circuit, triggering the circuit to apply electrical stimulation to the animal in the form of voltage pulses.
In order to be effective, an animal training collar must be able to deliver sufficient power to gain the animal's attention without injuring the animal. The necessary power level depends on the size of the animal, its level of activity, and the other stimuli competing with the trainer for the animal's attention. If the electrical stimulation applied to the animal has too little power, the animal will not respond and the collar will be ineffective for training purposes. On the other hand, if the power level is set too high, the animal may be injured or sufficiently frightened that it will refuse to respond to the trainer at all. Conventional animal training collars provide only limited control over the power of the electrical stimulus provided to the animal being trained, and are thus of limited value for training purposes.
Space and weight constraints limit known animal training collar to providing only a few levels of electrical stimulation to the animal. Each known device includes a transistor switch that controls the current in the primary of a transformer, the secondary of which forms the electrodes of the training collar. Trains of voltage pulses are applied to the input of the transistor switch, and the level of electrical stimulation at the electrodes is adjusted by altering the height (voltage) of the pulses, the frequency with which the pulses are delivered to the transistor switch, or the duration (time) that the voltage pulse train is applied to the transistor switch.
For example, one device drives the transistor switch with a fixed frequency train of voltage pulses, each pulse having a fixed pulse height (voltages) and pulse width. The stimulation level is adjusted by changing the DC bias at the transistor switch so that the effective voltage driving the transistor switch is adjusted to one of several levels. The number of different voltage levels that can be selected is thus limited by the number of different bias circuits that can be connected to the input of the transistor switch.
Another device, disclosed in U.S. Pat. No. 4,802,482, uses trains of voltage pulses having fixed voltages, pulse-widths, and frequency to control the transistor switch. In this case, the stimulus power is adjusted by increasing or decreasing the duration (length) of the pulse train, which increases the number of fixed voltage pulses generated at the electrodes. For this purpose, the electrical circuit includes a gated oscillator circuit having a selected frequency. The input of oscillator is driven by one of three RC circuit elements selected by signals from the trainer's transmitter and the output is coupled to the transistor switch. The length of the pulse train applied to the electrodes is adjusted by applying a signal voltage to the oscillator input through one of the RC circuit elements.
U.S. Pat. No. 5,054,428 discloses a training collar in which the strength of the electrical stimulus is adjusted by driving the transistor switch with trains of voltage pulses having different frequencies. For this purpose, the collar includes a circuit in which one of three different gated oscillators, each having a different oscillation frequency, is coupled to the transistor switch.
In these devices, the level of stimulation is selected by driving the transistor switch with circuits capable of producing only a few different voltage pulse trains. For example, the number of stimulation levels in the first device is set by the number of different bias circuits present in the collar circuitry. In the '482 patent, this number is determined by the number of RC circuit elements, and, in the '428 patent, this number is determined by the number of gated oscillators in the circuit. Due to the limited space available in a collar and the need to provide lightweight devices, there are limits to the number of circuit elements that can be added to the collar. Consequently, these approaches limit the number of different power levels available to the trainer for controlling the animal.
There is thus a need for an animal training collar that can provide greater control over the level of electrical stimulation applied to an animal in training.